Boreholes are drilled into the earth for many applications such as hydrocarbon production, geothermal production, and carbon dioxide sequestration. In order to efficiently use expensive resources drilling the boreholes, it is important for analysts to acquire detailed information related to the geologic formations being drilled.
Various types of tools referred to as downhole tools may be conveyed through the boreholes to perform various types of measurements to provide the analysts with the needed information. In order to make efficient use of drilling time, some downhole tools may be disposed on a drill string drilling a borehole so that measurements can be performed while the borehole is being drilled. These types of measurements may be referred to a logging-while-drilling or measurement-while-drilling.
Once the measurements are obtained, they can be transmitted by telemetry to a receiver at the surface of the earth so that they can be made quickly available to the analysts without having to remove the drill string from the borehole. One type of telemetry for while-drilling applications is mud-pulse telemetry. In mud-pulse telemetry, downhole data is encoded into a digital format and transmitted by pressure pulses in drilling mud filling the borehole or interior of the drill string. Power for the mud-pulse telemetry and downhole tools is generally electricity that is generated downhole. Hence, the drilling industry would appreciate any improvements in systems and methods to generate electricity downhole.